- It's open source, which means it's completely free.
- It supports most archive format, including 7z, ZIP, GZIP, BZIP2, TAR and RAR.
- it integrates into the windows explorer.
- It has 63 language support.
An interesting thing is, the english version of 7-Zip website doesn't provide the beautiful icon set that is available to chinese users.
So here it is:
for v4.2: http://www.7-zip.org/zh-cn/7z_iconset.exe
for v4.53: http://www.7-zip.org/zh-cn/7z-iconset-453.exe
Just download it according to your 7-Zip version and install it.